Neptune is the furthest planet from the Sun - but it may have formed much closer to the Sun before moving to its present position.
Neptune rotates on its axis incredibly quickly - its equatorial clouds take only 18 hours to make one rotation - and it's also the smallest of the class of planets known as the "ice giants". Despite being smaller than Uranus, Neptune has a greater mass.
It also has a very thin collection of rings and has 14 moons. One moon, Triton, is a volcanic icy world and was recently discovered to have seasons.
Why is Neptune so blue?
Neptune's atmosphere is made up of hydrogen, helium and methane gases. Methane absorbs red light, so the planet has a rich blue hue. Below its atmosphere, you'd find a layer of water, ammonia and methane ice and the inner core is made up of rock.
The planet also has a very active climate. A large storm was recorded on its surface in 1989 (and can be seen in the above image) - it was called the Great Dark Spot and lasted approximately five years.
The Great Dark Spot was discovered by the Voyager 2 spacecraft, which is the only craft to have flown by the planet. The Hubble Space Telescope has also studied Neptune, as have many ground-based telescopes. In fact, a strange storm that's as wide as the Earth has recently been spotted on Neptune by the Keck Observatory in Hawaii.
Extra reading and watching
Believe it or not, scientists have theorised that Neptune and Uranus could produce "diamond rain" thanks to the combination of the high temperatures and pressures, and the hydrocarbons present on both planets.
It may sound a bit far-fetched, but this process has recently been reproduced in the lab. Unfortunately, the lab-produced diamonds were only a few nanometres thick - but Neptune and Uranus's diamonds could be far bigger.
And here's a great video on the blue planet from Astrum:
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